Feingold proposes third-party money pledge

MADISON, Wis. (AP) -- Democrat Russ Feingold is proposing that Republican U.S. Sen. Ron Johnson agree to a campaign pledge to keep third-party money out of their U.S. Senate race in Wisconsin.

Feingold's campaign provided The Associated Press a copy of the pledge on Friday. The proposal is similar to the pledge that Democrat Elizabeth Warren and Republican Scott Brown agreed to in the 2012 Massachusetts Senate race.

Feingold gave Johnson's campaign the pledge just minutes after providing it to the AP. Johnson's campaign spokeswoman had no immediate comment.

Feingold says in a statement that the goal is to "limit the tens of millions of dollars from outside Super PACs and dark money groups on both sides of the aisle."